The present invention relates to a thin film transistor, particularly to one using low-temperature polycrystalline silicon, flat panel display devices using such a thin film transistor, such as liquid crystal display device and electron luminescence display device, and a method of manufacturing them.
Hitherto, thin film transistor devices used for flat panel displays have been manufactured, as for instance described in (1) '99 Latest Liquid Crystal Processing Techniques (Nikkei B P, 1999), pp. 53–59 (especially page 54), by forming an amorphous silicon film on a glass substrate by PE-CVD (plasma enhanced chemical vapor deposition), subjecting this amorphous silicon film to dehydration annealing for reducing hydrogen contained in the film, and then further subjecting it to excimer laser annealing to make the film polycrystalline.
According to the method of forming a crystalline semiconductor film described in (2) JP-A-11-354801, an oxide film is formed on an amorphous silicon film after cleaning this silicon film with an ozone-containing solution, then the oxide film is removed with a fluoric acid solution, and thereafter the silicon film is subjected to laser annealing to obtain a polycrystalline silicon film free of or minimized in surface protrusions. Any of these polycrystalline silicon films, however, fell short of providing a satisfactory result.